/usr/lib/swi-prolog/doc/Manual/hooks.html

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<H2><A NAME="sec:2.12"><SPAN class="sec-nr">2.12</SPAN> <SPAN class="sec-title">An 
overview of hook predicates</SPAN></A></H2>

<A NAME="sec:hooks"></A>

<P><A NAME="idx:hooks:170"></A>SWI-Prolog provides a large number of 
hooks, mainly to control handling messages, debugging, startup, 
shut-down, macro-expansion, etc. Below is a summary of all defined hooks 
with an indication of their portability.

<P>
<UL class="latex">
<LI><I>portray/1</I><BR>
Hook into <A NAME="idx:writeterm3:171"></A><A class="pred" href="termrw.html#write_term/3">write_term/3</A> 
to alter the way terms are printed (ISO).
<LI><I>message_hook/3</I><BR>
Hook into <A NAME="idx:printmessage2:172"></A><A class="pred" href="exception.html#print_message/2">print_message/2</A> 
to alter the way system messages are printed (Quintus/SICStus).
<LI><I>library_directory/1</I><BR>
Hook into <A NAME="idx:absolutefilename3:173"></A><A class="pred" href="files.html#absolute_file_name/3">absolute_file_name/3</A> 
to define new library directories. (most Prolog system).
<LI><I>file_search_path/2</I><BR>
Hook into <A NAME="idx:absolutefilename3:174"></A><A class="pred" href="files.html#absolute_file_name/3">absolute_file_name/3</A> 
to define new search-paths (Quintus/SICStus).
<LI><I>term_expansion/2</I><BR>
Hook into <A NAME="idx:loadfiles2:175"></A><A class="pred" href="consulting.html#load_files/2">load_files/2</A> 
to modify read terms before they are compiled (macro-processing) (most 
Prolog system).
<LI><I>goal_expansion/2</I><BR>
Same as <A NAME="idx:termexpansion2:176"></A><A class="pred" href="consulting.html#term_expansion/2">term_expansion/2</A> 
for individual goals (SICStus).
<LI><I>prolog_load_file/2</I><BR>
Hook into <A NAME="idx:loadfiles2:177"></A><A class="pred" href="consulting.html#load_files/2">load_files/2</A> 
to load other data-formats for Prolog sources from `non-file' resources. 
The <A NAME="idx:loadfiles2:178"></A><A class="pred" href="consulting.html#load_files/2">load_files/2</A> 
predicate is the ancestor of <A NAME="idx:consult1:179"></A><A class="pred" href="consulting.html#consult/1">consult/1</A>, <A NAME="idx:usemodule1:180"></A><A class="pred" href="import.html#use_module/1">use_module/1</A>, 
etc.
<LI><I>prolog_edit:locate/3</I><BR>
Hook into <A NAME="idx:edit1:181"></A><A class="pred" href="listing.html#edit/1">edit/1</A> 
to locate objects (SWI).
<LI><I>prolog_edit:edit_source/1</I><BR>
Hook into <A NAME="idx:edit1:182"></A><A class="pred" href="listing.html#edit/1">edit/1</A> 
to call some internal editor (SWI).
<LI><I>prolog_edit:edit_command/2</I><BR>
Hook into <A NAME="idx:edit1:183"></A><A class="pred" href="listing.html#edit/1">edit/1</A> 
to define the external editor to use (SWI).
<LI><I>prolog_list_goal/1</I><BR>
Hook into the tracer to list the code associated to a particular goal 
(SWI).
<LI><I>prolog_trace_interception/4</I><BR>
Hook into the tracer to handle trace-events (SWI).
<LI><I>prolog:debug_control_hook/1</I><BR>
Hook in <A NAME="idx:spy1:184"></A><A class="pred" href="debugger.html#spy/1">spy/1</A>, <A NAME="idx:nospy1:185"></A><A class="pred" href="debugger.html#nospy/1">nospy/1</A>, <A NAME="idx:nospyall0:186"></A><A class="pred" href="debugger.html#nospyall/0">nospyall/0</A> 
and <A NAME="idx:debugging0:187"></A><A class="pred" href="debugger.html#debugging/0">debugging/0</A> 
to extend these control-predicates to higher-level libraries.
<LI><I>prolog:help_hook/1</I><BR>
Hook in <A NAME="idx:help0:188"></A><A class="pred" href="help.html#help/0">help/0</A>, <A NAME="idx:help1:189"></A><A class="pred" href="help.html#help/1">help/1</A> 
and <A NAME="idx:apropos1:190"></A><A class="pred" href="help.html#apropos/1">apropos/1</A> 
to extend the help-system.
<LI><I>resource/3</I><BR>
Defines a new resource (not really a hook, but similar) (SWI).
<LI><I>exception/3</I><BR>
Old attempt to a generic hook mechanism. Handles undefined predicates 
(SWI).
<LI><I>attr_unify_hook/2</I><BR>
Unification hook for attributed variables. Can be defined in any module. 
See <A class="sec" href="attvar.html">section 6.1</A> for details.
</UL>

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swi-prolog-nox 5.10.4-3ubuntu1 / usr / lib / swi-prolog / doc / Manual / hooks.html
